1.1 What is Chemistry?

http://www.ck12.org Chapter 23. Electrochemistry

FIGURE 23.2

A drawing of Alessandro Volta’s voltaic pile, the first electric battery. It was

built of many individual cells, each consisting of a disk of copper or silver

and a disk of zinc separated by a cloth soaked in acid or brine. A 23-cell

pile like this would have produced around 36 volts.

FIGURE 23.3

Car battery

Pb+PbO 2 +2H 2 SO 4 →2PbSO 4 +2H 2 O

If we were to assign oxidation numbers to each atom, we would see that the only element changing state is lead. The
pure lead (oxidation state = 0) is oxidized to Pb^2 +, and the lead (IV) oxide (oxidation state = +4) is reduced to Pb^2 +.
We can therefore write the following two half-reactions:

Pb^0 →Pb^2 ++ 2e−

Pb^4 ++ 2e−→Pb^2 +

By separating the Pb^0 from the Pb^4 +, we can force the electrons to flow through a wire in order to complete the